Objectives: We reviewed our series of patients who underwent open abdominal aortic aneurysm (AAA) repair and constructed a prediction model for postoperative delirium.Methods: 397 patients who underwent open AAA repair at our institution between April 2005 and June 2013 were retrospectively reviewed. Postoperative delirium was diagnosed from the patients’ medical records according to the Diagnostic and Statistical Manual of Mental Disorders 4th Edition (DSM-IV) criteria. Mental alterations resulting from postoperative cerebrovascular events or preexisting mental disorders were excluded. Parameters with significant differences on univariate analysis were subjected to a logistic regression analysis.Results: There were 46 patients (11.5%) diagnosed with postoperative delirium. The following parameters were significant in the univariate analysis: age, history of stroke, hyperlipidemia, forced expiratory volume in 1 s (FEV1), percent vital capacity (%VC), and blood urea nitrogen (BUN) level. A logistic regression analysis revealed that an age ≥70 years (odds ratio [95% confidence interval], 3.342 [1.437–7.774]), blood loss ≥1517 mL (2.707 [1.359–5.391]), and the absence of hyperlipidemia (2.154 [1.060–4.374]) were significant risk factors.Conclusions: Older patients with substantial intraoperative blood loss require highly vigilant postoperative care. Further studies are necessary to elucidate the relationship between cholesterol and delirium.